NSC 40 No top end RPM'S

[nakman8]

Nissan NSC 40 outboard. Starts and and idles fine<br />Trolls for hours no problem. But when I go to full throttle I don't seem to get alot of power or rpms. It doesn't hesitate or miss and I have new plugs. Motor is installed on a 16.3ft fiberglass Glastron. Could my six month old gas be the problem? Am I pushing too big of a boat for the motor? <br />Thanks for any help

 

[TOHATSU GURU]

Re: NSC 40 No top end RPM'S

That's a common symtom for a variety of causes, but the most likely causes, in order of being encountered most often, are:<br />bad spark plug<br />carb high speed jet clogged<br />weak spark<br />low compression on one cylinder<br /><br />The weird things:<br /><br />bad bearings in lower unit(causes binding at high RPM<br />engine cover latch grounding to spark plug<br /><br />And it could be your old gas, do not use gas older than 3 months, your prop could be too high in pitch, the engine could be too small for the boat(a real possibility in your case) and you might have water trapped in the double bottom of your boat.